UK Pat. specification No. 1,204,123 (Unilever) discloses and claims detergent compositions and a process for their preparation in which sensitive ingredients are incorporated in granules throughout each of which the sensitive ingredient is dispersed. It has now been found that this and similar techniques are particularly advantageous with anti-redeposition agents.
Anti-redeposition agents are known ingredients in washing compositions. Reference can be made to Schwartz et al., Surface Active Agents and Detergents, Vol. II, Interscience Publishers Inc., N.Y., 1958, particularly pages 302-307. As there explained, anti-redeposition agents act to reduce the tendency for soil suspended in the wash-liquor to deposit on wash articles. Such anti-redeposition agents are usually polymers containing hydrophilic groups. Examples, see also Schwartz et al. cited above, include sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohols, partially hydrolysed polyvinyl acetates and alginates.
Within the last few years classes of anti-redeposition agents have been found that have a special, additional function: once deposited on clothes made from a fibre they reduce somewhat the tendency of the clothes to soil and they ease the removal in a subsequent wash of any soiling, particularly oily soiling, that does occur. They are soild release agents as well as anti-redeposition agents.
Such a soil-release agent is usually, but not necessarily, a polycondensate containing a hydrophilic group and a hydrophobic repeating group. The hydrophobic repeating group is preferably one that occurs in a fibre used to make clothes. Preferred soil-release agents are the agents developed by I.C.I. Ltd. of which some are sold under the trade-name Permalose. The preparation, structure, properties and uses of these preferred agents are described in U.K. Pat. specifications Nos. 1,088,984, 1,108,811, 1,108,812, 1,124,271, and 1,154,730 and Netherlands Pat. application No. 6614134 (all I.C.I.).
Another preferred class of compounds that has been found to have soil-release properties as well as anti-redeposition properties is celluloses containing an etherlinked, unsubstituted short-chain (e.g. C.sub.1 to C.sub.4) alkyl group and preferably also an ether-linked substituent based on a short-chain (e.g. C.sub.2 to C.sub.4) hydroxy alkyl group. Preferred examples of such compounds are described in Netherlands Pat. application Ser. No. 7110635 (Unilever) and U.S. Pat. No. 3,668,000 (Celanese Corporation). They are soil-release agents for synthetic materials. It will be appreciated that the ether-linked substituent based on a short-chain hydroxy alkyl group, as for example in Netherlands Pat. No. 7110635 or U.S. Pat. No. 3,668,000, can be a polymer formed, for instance, by condensing ethylene oxide or propylene oxide with the cellulose.
The preferred compound of U.S. Pat. No. 3,668,000 is hydroxy propyl methyl cellulose as there described. The preferred compounds of Netherlands Pat. No. 7110635 are, as there described, celluloses in which the total number of substituent groups per glucose unit of a cellulose derivative should be between about 1.5 and about 3.0, preferably between about 2.0 and about 3.0. There should be at least about 1.0, preferably from about 1.0 to about 2.5, and particularly preferably from about 1.5 to about 2.1, alkyl groups per glucose unit; and at least about 0.1, preferably from about 0.2 to about 1.5, and particularly preferably from about 0.5 to about 1.5, hydroxyalkyl groups per glucose unit. The alkyl groups should contain from 1 to 4, and preferably from 1 to 3, carbon atoms, and the hydroxyalkyl groups should contain from 2 to 4, preferably from 2 to 3, carbon atoms. Particularly preferred alkyl groups are methyl and ethyl, and the preferred hydroxyalkyl groups are hydroxyethyl and hydroxypropyl. Propyl, butyl and hydroxybutyl groups may also be used. When the alkyl group is methyl it is preferred that the hydroxyalkyl group be hydroxypropyl, and when the alkyl group is ethyl it is preferred that the hydroxyalkyl group be hydroxyethyl, although it will be appreciated that other combinations of alkyl and hydroxyalkyl groups may be used if desired. Particularly preferred cellulose derivatives for use in accordance with the invention are methyl hydroxypropyl celluloses having from 1.7 to 2.1 methyl groups per glucose unit and from 0.8 to 1.0 hydroxypropyl groups per glucose unit, and ethyl hydroxyethyl celluloses having from 1.5 to 1.6 ethyl groups per glucose unit and from 0.5 to 0.6 hyroxyethyl groups per glucose unit.
Many of these cellulose derivatives are available commercially, and others can readily be prepared by simple chemical procedures. For instance, a methyl hydroxypropyl cellulose derivative can be prepared by reacting the cellulose with dimethylsulphate and then with propylene oxide (or vice versa: if one substituent is to be present in a greater amount than the other, it is preferable that the major substituent is applied first), and an ethyl hydroxyethyl cellulose can be prepared by reacting the cellulose with ethylene oxide and then with ethyl chloride.